MdePkg/BaseLib: RISC-V: Support getting satp register value

Add an API to retrieve satp register value.

Signed-off-by: Tuan Phan <tphan@ventanamicro.com>
Reviewed-by: Andrei Warkentin <andrei.warkentin@intel.com>
Reviewed-by: Sunil V L <sunilvl@ventanamicro.com>

MdePkg/Include/Library/BaseLib.h

@@ -181,6 +181,11 @@ RiscVSetSupervisorAddressTranslationRegister (
   IN UINT64
   );
 
+UINT64
+RiscVGetSupervisorAddressTranslationRegister (
+  VOID
+  );
+
 UINT64
 RiscVReadTimer (
   VOID

MdePkg/Library/BaseLib/RiscV64/RiscVMmu.S

@@ -21,3 +21,11 @@
 ASM_FUNC (RiscVSetSupervisorAddressTranslationRegister)
     csrw  CSR_SATP, a0
     ret
+
+//
+// Get the value of Supervisor Address Translation and
+// Protection Register.
+//
+ASM_FUNC (RiscVGetSupervisorAddressTranslationRegister)
+    csrr  a0, CSR_SATP
+    ret